This invention relates to a method of transferring a discrete portion of a first web onto a second web. More particularly, this invention relates to a method of transferring a discrete portion of a first web onto a second web even when the first and second webs are traveling at different speeds.
In today""s consumer market, there are numerous types of products which require that a discrete portion of a first web be transferred, aligned and/or attached to a second web to make a composite article. Many times, the first and second webs are traveling at different speeds and the transfer has to take place at high speeds. Disposable absorbent articles, such as diapers, training pants, sanitary napkins, pantyliners and incontinence products, including undergarments, briefs, pants and pads, are representative products which rely on the merging of discrete portions of one web with a second continuous web. Many times, it is necessary to transfer, align and/or attach a discrete portion of a first web to a second web at speeds exceeding 100 feet per minute (3048 cm/min.). The attachment of a discrete portion of a first web onto a second web can be accomplished by various means including an adhesive, a mechanical connection, by forming a bond using heat and/or pressure, by forming an ultrasonic bond, etc. Hot or cold melt adhesives and ultrasonic bonds are the most commonly used forms of attachment.
Some disposable absorbent articles, such as sanitary napkins and incontinence pads, also rely on a garment attachment adhesive to secure the article to the inside surface of the user""s undergarment. The garment attachment adhesive can be applied to the bottom surface of the article and is normally covered by a releasable liner or backing material. The releasable liner will prevent the garment attachment adhesive from becoming contaminated prior to use. Prior to use of the article, the consumer will remove the releasable liner. The mating of the releasable liner to the article is another example where a discrete portion of a first web needs to be brought into registration and alignment with a second web.
Many articles found in today""s retail outlets, supermarkets and grocery stores require a label that notifies the consumer of the product inside the container or package. The label can provide useful information to the ultimate consumer. Some labels are required by law to provide a description of the ingredients or to ensure the consumer that the product has not been previously opened. Many such labels are secured to an outside surface of the container or package using an adhesive. Many other kinds of labels, such as mailing labels, name tags, etc. need to be adhered to the container or package just prior to shipment. Most of these labels are adhered to an outer surface of the container or package by an adhesive or glue. Attachment of such labels by high-speed equipment can utilize the present invention.
It should be noted that the list of items requiring a discrete portion of a first web, layer of material or composite member to be brought into contact and perhaps be secured to a second web is endless. Consumer goods of all kind can possibly take advantage of the present invention. The discrete portion, which can be transferred to a second web, can be made of almost any kind of material.
The production machinery for attaching a discrete portion of a first web to a second web can generally be described as an apparatus having a cutting mechanism and various rolls or rollers. Typically, the first web is a continuous roll of material that is advanced to a converting mechanism. One or more feed rolls may be used to advance the first web. The speed of the feed rolls determines the speed at which the first web is supplied to the converting mechanism. The converting mechanism can be a cutter capable of slitting, cutting or severing a discrete portion from the first web. The discrete portion will have a desired shape and size. In many cases, the cutting is performed as the first web is advanced through a nip formed by a rotary knife that comes into close proximity or contact with an anvil or backup roll. The discrete portion of the first web is then carried via various rolls, typically vacuum rolls, to a location where the discrete portion can be transferred to the second web.
In general, such converting mechanisms and transfer rolls are designed to operate at a constant speed to cut a particular size discrete portion from a first web and transfer it to a second web. Mechanical mechanisms such as gears, belts and chains are conventionally used to synchronize the first web, the cutting mechanism, the transport rolls and the second web.
When the dimensions of the discrete portion are changed, it is generally required to change some of the components of the converting mechanism and transfer rolls. With each component change, large amounts of money can be lost due to the downtime required to make the change, in addition to the capital invested in multiple grade change components.
One method used to avoid having to reengineer the machinery for each change made to the product is to run the apparatus at different speeds depending on the size of the discrete portion needed to be transferred to the second web. For example, if a longer discrete portion is needed, the rate at which the first web is advanced to the converting mechanism is increased. However, by increasing the speed of the first web, the transfer of the discrete portion onto the second web will no longer occur at the same speed and/or at the desired interval.
When two webs of materials are joined at different speeds, there is a tendency for the materials to experience shock loads, pulling, wrinkles and gaps. In most applications, joining two webs traveling at different speeds can have drastic effects on a fast moving, continuous process. Another problem caused by mismatched web speeds is that as the discrete portion of the first web contacts the second web, a jarring or shocking action may occur. This action can cause at least one of the webs to rip, tear, or wrinkle. A torn web generally requires stopping the machine and rethreading the incoming web around the guide rolls and through the various nips. In a worst case scenario, the machine may be damaged and certain parts may need to be repaired and/or replaced.
There have been a vast number of attempts made at bringing together two webs traveling at the same or at different speeds, and combining them to provide a single combined web. To date, most methods lack full acceptance for one or more reasons.
Now a method has been invented which allows a discrete portion of a first web traveling at a first speed to be successfully transferred to a second web that is traveling at a second speed.
Briefly, this invention relates to a method of transferring a discrete portion of a first web onto a second web. The method includes advancing the first web at a first speed and advancing the second web at a second speed. The first web is directed to a converting mechanism where a discrete portion is formed. The discrete portion is then transferred onto a vacuum roll that is traveling at a rotational speed equal to or greater than the first speed. The method further includes transferring the discrete portion from the vacuum anvil roll onto a transfer roll that is traveling at the speed of the vacuum anvil roll. The transfer roll is driven by a servomotor and is capable of changing speeds. The speed of the transfer roll is varied to match the speed of the second web and the discrete portion is transferred onto the second web.
The general object of this invention is to provide a method of transferring a discrete portion of a first web onto a second web. A more specific object of this invention is to provide a method of transferring a discrete portion of a first web onto a second web when the first and second webs are traveling at different speeds.
Another object of this invention is to provide a method of making a matched speed transfer of a discrete portion of a first web traveling at a first speed onto a second web traveling at a second speed.
Still another object of this invention is to provide a method of transferring and attaching a discrete portion of a first web onto a second web when the two webs are traveling at different speeds.
Still further, an object of this invention is to provide a method of transferring a discrete portion of a first web traveling at a first speed onto a second web traveling at a second speed while greatly reducing induced stresses in the webs.
Still further, another object of this invention is to provide an economical and efficient method of transferring and attaching a discrete portion of a first web onto a second web when the two webs are traveling at the same or at different speeds.
Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the accompanying drawings.